Cryoglobulinemia: An update on classification, pathophysiology, clinical presentation, and management.

Cryoglobulinemia (CG) is defined by the presence of serum immunoglobulins that precipitate below 37°C and redissolve upon rewarming. It is classified into three types based on immunoglobulin composition. Type I, a rare form, involves monoclonal IgM or IgG and is linked to lymphoproliferative disorders. Types II and III are known as mixed CG (MC): Type II consists of polyclonal IgG and monoclonal IgM with rheumatoid factor (RF) activity, whereas Type III includes polyclonal IgG and polyclonal IgM with RF activity. MC is predominantly associated with hepatitis C virus (HCV) infection and involves B-cell lymphoproliferation and autoantibody production. CG may lead to systemic vasculopathy, ranging from mild symptoms (purpura, asthenia, and arthralgia) to severe complications such as skin ulcers, peripheral neuropathy, renal involvement, and non-Hodgkin lymphoma. Compared to MC, Type I is more often marked by severe cutaneous involvement (ulcers, gangrene), hyperviscosity, and a higher risk of morbidity due to the underlying hematologic malignancy. Management of Type I requires control of vasculopathy and treatment of the hematologic neoplasm, whereas MC demands antiviral therapy in all HCV-associated or hepatitis B virus-associated cases. Severe vasculopathy in both types may benefit from corticosteroids, immunomodulators, anti-CD20 monoclonal antibodies, and plasma exchange. A multidisciplinary approach is essential for addressing both etiology and complications, thereby improving outcomes. This review summarizes the pathophysiology, clinical features, recent etiopathogenetic insights, and therapeutic advances related to the various forms of CG.